Northstar Engines and System Technical Discussion Discussion, High Mileage Northstar Thread: Who can beat me? in Cadillac Engine Discussion; Please do some searching before starting another thread on a subject that is, and has, been covered extensively.
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Re: High Mileage Northstar Thread: Who can beat me?

Is this engine still intact for all these miles? What major components have you replaced? And how is the transmission holding up? Do you use an oil additive? My '96 STS is at 426k...transmission went out at 377k.....just curious about your experience! Thanks,STS777.

Re: High Mileage Northstar Thread: Who can beat me?

Just bought a 2001 Seville STS, 87,000 miles..rides like it's on a cloud and fast, too!
Unrelated, my 1993 Seville 4.9L has 143,000 but will need a new motor unfortunately...she's going into storage until I can get her a new motor.

Re: High Mileage Northstar Thread: Who can beat me?

i think the shocking part is that there is not a single dummy light on like that guy on youtube driving around in his high mileage caddy with messages chimming on the dash and all the lights going crazy

Re: High Mileage Northstar Thread: Who can beat me?

Are you still under the impression that there is anything wrong with properly maintained DEX-COOL ? Your question would appear so .........

Here's 2 quarts of 50/50 DEX-COOL from the truck engine with 88,900 miles on it (the engine) - the coolant is 3.5 years old. Just changed it all. Look like anything wrong there ?????

It looks beautiful--almost good enough to drink! (edit: make sure to put skull and crossbones on it if you have any children in the family). Alas, I'm not concerned about the coolant itself more so than the head gasket. Tearing the engine down and looking at the head gasket would give a better picture of how well it is protecting it.

The silicates in conventional green coolant coat carbon/carbon composites [graphite composite headgasket] and are used to make it oxidation resistant. Dex-Cool is a silicate-free coolant. It is wonderful in protecting aluminum, brass, cast iron, steel and copper, but offers no carbon/carbon protection. Our composite head gaskets are made of graphite (carbon), copper/brass, and felt, and a good portion of them are soaked in coolant.

Other large manufacturers saw this protection void (and the lawsuit due to deterioration of silicone rubber and nylon gaskets), and opted to add silicates to their versions of long-life coolants, and they are now called Hybrid organic acid technology coolants. The added silicates coat and protect what the potassium 2-ethylhexaonate (hexaonic acid) doesn't. Toyota, Honda, Ford and probably others use this type of hybrid coolant. They prohibit the use of anything else, quite emphatically in some instances.

How many 93-96 Northstar's have HG failure vs 97-99 before the better headbolts? They are otherwise virtually the same engine--are they not??

**edit: I'm not saying that there aren't any failures on 93-96 or that the observation negates the other flaws such as torque-to-yield head bolts, or a flaky gaskets. I'm saying those head gaskets may be very vulnerable to fail in as it is with all the expanding and contracting cycles of the aluminum or the graphite and the steel bolts... The straw that breaks the camel's back or rather precipitates the failure could be a coolant that lacks corrosion/oxidation protection to graphite. A renowned polymer expert I work with confirmed it for me: graphite does in fact corrode/oxidize readily if uncoated, it burns or flakes.